Parallel invocation of edge servers within a Web infrastructure has been shown to provide benefits, in terms of system responsiveness, for both content delivery applications and non-transactional Web services. This is achieved thanks to the exploitation of path-diversity proper of multi-hop networks over the Internet, which typically reduces the likelihood of client perceived link congestion. In this work we address parallel invocation of geographically spread edge servers in the context of transactional Web-based applications. Actually, parallel invocation protocols are not trivial for this type of applications, since we need to deal with a set of issues not present in classical content delivery applications, such as (i) non-idempotent business logic and (ii) increase of the workload on the data centers. In this paper we propose a simple and lightweight parallel invocation protocol for distributed transactions over the Web, which addresses all those issues in a scalable manner by requiring no form of coordination among (geographically spread) edge servers. The results of a simulation study are also reported to show the advantages from our protocol in terms of user-perceived system responsiveness.